An international team of researchers has found that Antarctic krill could be vital in the fertilization of the Southern Ocean with iron and thereby the stimulation of phytoplankton growth. This enrichment betters the ocean’s ability to store CO2.

The tiny shrimp-like crustacean is the staple diet for various fish, penguins, seals and whales, as well as being caught by commercial fisheries for human consumption by way of omega-3-rich krill oil and other products.

In findings published this month in the journal Limnology and Oceanography, researchers describe how Antarctic krill (Euphausia superba), instead of residing mostly in surface waters, regularly spend time on the sea floor feeding on iron-rich fragments of decaying organisms. The krill then swim back up to the surface of the ocean and release the iron from their stomachs and into the water.

"We are really excited to make this discovery because the textbooks state krill live mainly in surface waters,” said lead author from British Antarctic Survey Dr Katrin Schmidt.

“We knew they make occasional visits to the sea floor but these were always thought as exceptional. What surprises us is how common these visits are – up to 20 per cent of the population can be migrating up and down the water column at any one time," she noted.

The team of researchers dissected the stomach contents of more than 1,000 krill harvested from 10 Antarctic research expeditions and discovered that the krill caught near the surface contained high levels of iron-rich material from the seabed in their stomachs.

Plus, the scientists studied photographs of krill on the sea floor, acoustic data and net samples, all of which gave sturdy evidence that the crustaceans frequently feed at the bottom of the sea.

These recent findings have implications for managing commercial krill fisheries and can help better comprehend the natural carbon cycle in Antarctica’s Southern Ocean.

“The next steps are to look at exactly how this iron is released into the water," Schmidt added.

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